The linear alternating copolymers of carbon monoxide and aliphatic .alpha.-olefins of at least 3 carbon atoms are known in the art. In copending U.S. patent application Ser. No. 442,089, filed Nov. 28, 1989, there are produced such polymers which are regioregular but stereo-irregular. Such polymers result from polymerization of carbon monoxide and an aliphatic .alpha.-olefin of at least 3 carbon atoms in the presence of a palladium compound, the anion of a strong non-hydrohalogenic acid and an aliphatic bidentate ligand of phosphorus such as 1,3-bis (di-n-butylphos-phino) propane. Alternatively, in copending U.S. patent application Ser. No. 352,235, filed May 25, 1989, there are produced such linear alternating polymers that are regioregular and stereoregular in the presence of a bidentate sulfer ligand. These polymers are produced by contacting the monomeric reactants in the presence of a catalyst composition formed from a palladium compound, the anion of a strong non-hydrohalogenic acid and a bidentate phosphorus ligand of the structure EQU R.sub.2 P--R'--PR.sub.2
where R, inter alia, is phenyl and R' is a cyclic bridging group of at least two carbon atoms. A specific example of this latter ligand is 4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane.
The term "regioregular" as applied to linear alternating polymers of carbon monoxide and aliphatic .alpha.-olefin of at least 3 carbon atoms refers to the manner in which the moieties derived from the .alpha.-olefin are attached to the moieties derived from the carbon monoxide. If the .alpha.-olefin moieties are attached to the carbon monoxide moieties in predominantly a head-to-tail manner, the polymer is termed regioregular. A polymer with less than a predominance of head-to-tail bonding is termed regio-irregular. The term "stereoregular" applies to the configuration of the adjacent asymmetric carbon atoms in the linear alternating polymers. Stereoregular character may be isotactic or syndiotactic. When the configuration of adjacent carbon atoms is the same, e.g., ##STR1## wherein R is alkyl and the wavy lines indicate the continuing polymer chain, the polymer is termed isotactic. However, when the configuration of adjacent asymmetric carbon atoms is opposite, e.g., ##STR2## the polymer is termed syndiotactic. A polymer in which there is no predominant or regular arrangement of asymmetric carbon atoms is termed stereo-irregular or atactic.
In practice, however, any given polymer will not be completely in either stereoregular form. If more than 50% of the adjacent asymmetric carbon atoms have the same configuration the polymer will be termed isotactic. In like manner, if more than 50% of the adjacent carbon atoms are oppositely configured, the polymer is termed syndiotactic. The average percentage of such carbon atoms of isotactic configuration or syndiotactic configuration is termed the average isotacticity or average syndiotacticity, respectively. As stated above, it is also possible to directly produce a linear alternating polymer of atactic character.
For some applications it is desirable to have a linear alternating copolymer of carbon monoxide and aliphatic .alpha.-olefin of at least 3 carbon atoms which is highly stereoregular. For other applications it is desirable to have a copolymer having a lower stereoregular character and thus a higher atactic character. It would be of advantage to provide a process whereby the stereoregular character of a linear alternating copolymer of carbon monoxide and aliphatic .alpha.-olefin of at least 3 carbon atoms could be decreased while increasing the atactic character of the resulting polymer.